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Fix Add.build_call_graph CNOT count for unequal register bitsizes #1986

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Fix Add.build_call_graph CNOT count for unequal register bitsizes #1986

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10 changes: 9 additions & 1 deletion qualtran/bloqs/arithmetic/addition.py
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Original file line number Diff line number Diff line change
Expand Up @@ -219,7 +219,15 @@ def decompose_from_registers(

def build_call_graph(self, ssa: 'SympySymbolAllocator') -> 'BloqCountDictT':
n = self.b_dtype.bitsize
n_cnot = (n - 2) * 6 + 3
m = self.a_dtype.bitsize
if not is_symbolic(n) and n == 1:
return {CNOT(): 1}
if m == n:
n_cnot: SymbolicInt = (n - 2) * 6 + 3
elif not is_symbolic(m) and not is_symbolic(n):
n_cnot = (n - 2) * 3 + 2 + 3 * m - 3
else:
n_cnot = (n - 2) * 3 + 2 + sympy.Piecewise((3 * n - 5, sympy.Eq(m, n)), (3 * m - 3, True))
return {And(): n - 1, And().adjoint(): n - 1, CNOT(): n_cnot}

def get_ctrl_system(self, ctrl_spec: 'CtrlSpec') -> Tuple['Bloq', 'AddControlledT']:
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11 changes: 11 additions & 0 deletions qualtran/bloqs/arithmetic/addition_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -205,6 +205,17 @@ def test_addition_gate_counts(n: int):
qlt_testing.assert_equivalent_bloq_counts(add, ignore_split_join)


@pytest.mark.parametrize(
"m,n",
[(a, b) for b in range(1, 7) for a in range(1, b + 1)],
)
def test_addition_gate_counts_unequal_bitsizes(m: int, n: int):
add = Add(QUInt(m), QUInt(n))
qlt_testing.assert_valid_bloq_decomposition(add)
assert add.t_complexity() == add.decompose_bloq().t_complexity()
qlt_testing.assert_equivalent_bloq_counts(add, ignore_split_join)


@pytest.mark.parametrize('a,b', itertools.product(range(2**3), repeat=2))
def test_add_tensor_contract(a, b):
num_bits = 5
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